Synthesis of ammonia from its elements



Patented Dec. 19, 1922;

. STATES 7 1,439,291 ATENT orrlca. F

g 7 JOHN COLLINS CLANGY, F NIAGARA FALLS, NEW YORK, ASSIGNOB TO THE NITBO' GEN'CORP ORATION, OF PROVIDENCE, RHODE ISLAND, A CORPOEATIOIT OF RHODE ISLAND.

SYNTHESIS OF AMMONIA FROMITS ELEHE VTS.

No Drawing.

To all whomit may concern: 7

Be it known that I, J OHN CoLLrNs CLANGY, a Subject of the King of Great Britain, miding at Niagara Falls, in the county of Niagara and State of New York, have invented certain new and useful Improvements in Snythesis of Ammonia from Its Elements, of which the following is a specification.

Ihis invention relates to the synthesis of 10 ammonia from its elements through the instrumentality of a catalyst possessing certain novel and particularly-valuable properties and characteristics.

My disclosure herein, also concerns the production of said catalyst; the principal objects of my invention being to reduce the cost of production of the catalytic material, while at the same time increasing its hardiness or durability and thereby increasing its life when in use.

These and other objects of said invention will be hereinafter referred to and thenovel combinations of steps in the process and of materials in the composition of matterwmch constitute the catalyst employed in said process, will be more especially pointed out in the claims appended hereto.

As I am aware of various modifications of and chan es in my process and preferred catalyst, desire to be limited onlyby the scope of said claims, broadly interpreted in the light of my disclosure.

In my application entitled: Ammonia synthesis and catalyst for effecting the same,-

Serial No; 346,320, filed December 20, 1919, I described a mode of producing active mate-- rial from complex cyanogen bearing compounds such as calcium ferrocyanid, barium ferrocyanid, or potassium ferricyanid, etc.

In said application, the desirability of employing a distributive support for the catalytic material proper, was'emphasized; as was also the mode of completing the preparation and, finally, the activating of said mai terial after the substance from which it was formed had been completely freed from water. The activation was accomplished by particular heat treatment while the catalyst was surrounded by an atmosphere of mixed '50 hydrogen and nitrogen.

I have now discovered that it is possible to start with identically the same substance, e. g.,'ca'lcium ferrocyanid,and by a somewhat analogous andyet essentially different Application filed January 7, 1920. Serial in. 349,953. 7

mode of treatment, produce a catalyst possessmg markedly. different properties. By way of illustration: Starting with a concentrated solution of calcium ferrocyanid in water and sulfur-free and otherwise clean P11111166 lumps, preferably of about the size of peas or a trifle larger, I immerse the pumice in the solution and evaporate off the water whlle stirring the mass constantly,

After the charge to be treated has been well drled, preferably at about 100 0., it is then first placed in a preparing'autoclave and its temperature is very gradually stepped up to about 350 (3., durlng the course of a number of hours.

The operation thus far may be, and, in fact, desirably is, conducted at atmospheric pressure and the charge under treatment may be conveniently maintained in an atmosphere of mixed hydrogen and nitrogen; although hydro en or nitrogen alone may be used. Air or ree oxygen is, in any case, excluded; especially as. the more elevated temperatures are approached, as even a trace of free oxygen or water is then highly 1njurious.

Thus far, the treatment corresponds closely with that which was described, to a like I in mode of operation and especially in results.

The heated material is now subjected to a current of ammonia gas, preferably under atmospheric pressure, to displace thehydrogen present in the pores'of said material, and the temperature is slowly raised to, say, 400 6., or more; but never desirably above 650 C. In this treatment the need'for great care in controlling the temperature, described in said application with special reference to the activation of the earlier catalyst, is however, now no longer required.

My new catalyst becomes active at a lower temperature than the one described in said application; to wit, at about 325 C.,' and it is capable of synthesizing ammonia from its elements even at this low temperature.

, Said catalyst may moreover, be improved by departing further from the described treatment.

Thus, if instead of initially preparing the catalytic material, or catalyst-to-be, in an atmosphere of the synthesizing gases, it is seriously impaire from 400 to 450 (3.,

subjected, evenwhile being treated in the preparing autoclave, to an atmosphere of ammonia vapor, it becomes more hardy and resistant to deterioration when in use.

In fact it is so hardy and non-pyrophoric that when cooled to room temperature, it does not ignite upon exposure to the air.

()n the other hand, the more sensitive catalyst (or class of catalysts) described in my said application, is highly pyrophoric after activation, perature.

The present non-pyrophoric catalyst, prepared as aforesaid,'may now be cooled and transferred to the working or synthesizing autoclave, with exclusion of air; but I prefer to eject it, While hot, directly from the preparing autoclave into the Working autoclave, by a jet of the synthesizing gases, air being of course carefully excluded during this transference.

The herein described treatment 'of the catalytic material, permits of elevating the temperature of the catalyst, under synthesizing conditions, to 500 C. or even to 600 and the catalyst is not injured thereby.

ere again, it distinguishes from my earlier catalyst, which if heated to, say, 550 C., and especially if heated above 600 C., under synthesizin conditions, becomes very or it may be ruined, if said temperature be maintained for but a few hours.

The present catalytic bodies are more easily controlled; there being ipracticallly never any tendenc for their temperatures to inadvertently ru up if merely reasonable care be exercised in the control of the exothermic synthesizing reaction. They can be handled with less care; being farless delicate. They actively synthesize ammonia at lower temperatures; the preferred temperature in the present case being about 400 C., or somewhat less, rather than 450 C.; which. of course, prolongs the life of the autoclave. The preferred operating pressure is about one hundred atmospheres.

When usingp'ure gases, the useful life of the catalyst described in my said application. is about twenty-five days, Whereas catalysts of the class herein described are available for use, operating commercially, for forty days or more.

The preparation of my said earlier discovered catalyst must be conducted-care fully and slowly; whereas the present catalyst, after the material from which it is formed in part, has been dried at temperatures ranging graduallynp from 100 C. to 150 C., may then be sub ected to the action of ammonia gas for but a few hours, at and thereupon be at once ready for the synthesizing operation.

The initial percentage yield from these catalysts, if both are operated at, say, 450

falls off more rapidly and it even when at room tem-' (3., under the same conditions, is about the same; but the yield of the earlier catalyst requlres occasionaI periods of rest; whereas the present ammonia-gas-treated catalyst does not thus tend to become fatigued, and itsyield holds up for a much longer time. Toward the end of its life, the yield gradually falls, while with the earliercatalyst, there is usually an ,abrupt drop in yield as the end ofits period of commercial usefulness is approached.

Also, the space-time yield of the new catalyst, herein described, is much greater; as the rate of flow of gases thereover can be greatly increased Without injury to the catalyst.

Again, the earlier catalyst requires a distributive support such as pumice lumps; since, otherwise, it is too concentrated and being very sensitive, becomes over-heated unless the proper control of the temperature, favored by the supportfis exercised. In the present catalyst, whil port or the like is desirable, to afford porosity and to economize catalytic material, said support is by no means essential, as no exothermic reaction is involved in its preparation.

The exact composition of the replacement compounds formed by thus reacting with ammonia gas upon cyanogen compounds, or mixtures of compounds or substances one at least of which has initially a high cyanogen content, is exceedingly diflicult to determine,

and I am of the opinion that it is quite complex; being possibly in the nature of a complex salt including the roups (CN') or (CN,), and (NH or (N At any rate, there appears to be present therein after the finished *product has been formed, not only nitrogendirectly united to carbon by a plurality of bonds; but also, nitrogen free from direct connection with carbon.

During the treatment with the ammonia gas, there is a tendency to replace some of the nitrogen-carbon radicals in the catalyst in course of preparation, with nitrogen united directly to hydrogen, and if. free hydrogen be present,. hydrocyanic acid gas will be formed. Much of the cyanogen content of the mass will remain therein, however, if the temperature of the operation be not too high; and When free cyanogen, or HCN, is no longer liberated at a given operating pressure the catalyst is ready for use.

By way of further illustration, it will be e the pumice supwell to state that when thus producing an 7 addition compound by means of ammonia, I may start with. not only the iron-cyanids previously-mentioned, but, also, with such double salts as:

Preferably, for convenience and cheapness of preparation of the catalyst, I start with Such compounds, or mixtures of substances as the foregoing; because'ef their solubility in water; although insoluble compounds The ammonia gas used in their treatment with non-harmful gas, such as the gaseous mixture of nitrogen and hydrogen used in the synthesizing operation; care being taken,

. is preferably pure; but it'may be diluted I of a catalyst whichincludes nitrogen united directly to hydrogen, and carbon united directly tonitrogen, an alkalinous metal and a less basic metal adapted to co-act with the aforesaid constituents to constitute an, active catalyst which is substantially free from any tendency to overheat when in use in the synthesizing operation.

3. The process of producing ammonia which comprises synthesizing said ammonia from its elements through the intermediacy of a catalyst consisting of a complex addition product resulting from the treatment of a doublev cyanogen salt with hot ammonia gas. I

4. The process of producing ammonia which comprises synthesizing said ammonia in -this case, to avoid such-an excessive di-.

lut-ion of the ammonia as would impair its action upon the material under treatment. In general, the more concentrated the ammonia, the better.

The term alkalinous metal as, used in certain of the appended claims is intended to refer to such metals as: calcium, strontium, barium, potassium, etc; this expression being employed to avoid circumlocution in said claims. I

Some of these metals are mode adapted to the production of an eflicient catalyst than others; the catalytically active metal, potassium, for example, being superior to sodium, andcalcium being, likevfisqgreatly to be preferred to magnesium. I have particularly specified the preferred metals of this type, because such specified metals are both very well adapted tothe purpose in I claim is:

question, and because, also, they are not rare or costly. Obviously this latter factor must be taken into consideration if the synthetic operation is to be of real value.

For analogous reasons, and because of the solubility of their cyanids, the auxiliary or less basic metal or metals, present in the complex catalyst, should desirably be either chromium, ironormanganese. Titanium,

forexample, is also well suited for use in in the presence of ammonia gas.-

from its elements through the intermediacy of a catalyst consisting of a complex addit-ion product resulting from the treatment of a double cyanogen salt with hot ammoniagas, one of the base forming constituents of said double salt being an alkalinous metal and another of said constituents being a materially less basic metal, ,substantially as of a catalyst consisting of a complex addition product resultin from the treatment ofa water-soluble doub e cyanogen salt with hot ammonia gas. I

6. The process of producing ammionia which comprises synthesizing said ammonia from its elements through the intermediacy of a highly porous catalytic body, the walls of the pores of which are coated with films of active catalytic material formed by reacting with ammonia gas upon cyanogen-bearing material in which abasic metal and a relatively non-basic metal are present, said basic metal being alkalinous in character.

, 7. The process of producing ammonia which comprises synthesizing said ammonia from its elements through the intermediacy' of active catalytic material formed by reacting with ammonia gas upon cyanogenbearing material in which a; basic metal and a relatively non-basic metal are present, said basic metal being alkalinousin character.

.8. The process of producing ammlonia which comprises synthesizing said ammonia ammonia from its elementsthrough the intermediacy of active catalytic material formed by re-, acting with ammonia gas ..upon cyanogenbearing material in which abasic metal I and chromium are present, said basic metal being alkalinous in character. 7

' 9. The procws 'of producing ammonia which comprises synthesizing said ammonia 2. The process of producing ammonia L which comprises synthesizing said amino ia from its elements through the inteimedia y from its elements by bringing-the elements into contact with a non-pyrophoriccatalyst formed from a cyanogen salt of an. alkalinous metal and subjecting saidelements to the influence of heat.

10. The process of producing ammonia, which comprises synthesizing said ammonia from its elements by bringing the elements into contact with a .catalytically active material formed by treating a cyanogen salt of an alkalinous metal with hot .ammonia as. g 11. The process of producing ammonia, which comprises synthesizing said ammonia from its elements by bringing the elements gas, and subjecting the said elements tothe influence of heat and pressure.

-In testimony whereof I have aflixed my signature in they presence of twowitnesses.

JOHN COLLINS CLAN CY.

Witnesses:

E. J. PARENT, ELSA VORWERT. 

